In an email to The Wall Street Journal, Nintendo spokesman Yasuhiro Minagawa on Monday reiterated previous company statements that the Japanese videogame giant hasn’t complained at all about Flappy Bird’s similarities to Nintendo’s original “Super Mario Bros.”

“While we usually do not comment on the rumors and speculations, we have already denied the speculation” last week, he said.

Created by Hanoi-based game developer Dong Nguyen, Flappy Bird had become the No. 1 free mobile game on Apple 's iTunes and Google 's Android Play store before it abruptly disappeared this past weekend.

“I cannot take this anymore,” Nguyen apparently wrote Sunday night on his unverified Twitter account. Nguyen has remained silent since the game disappeared, even as his Twitter followers have grown from several thousand to 121,000 in a matter of days.

An English-language Vietnamese media outlet, Tuoi Tre News, on Monday quoted a local technology observer as saying that Nguyen could face a copyright lawsuit over his game’s graphics; both feature green pipes that are similar in appearance.

Nguyen hasn’t answered questions emailed to him by the WSJ, after asking for time to review them.

Meanwhile, others have wondered if Nguyen may have removed the game because it violated Vietnam’s controversial new curbs on Internet use that went into effect in September. The rules limit online speech and require foreign companies to maintain at least one server in the country.

But Nguyen’s activities appear not have violated those rules, according to Tran Manh Hung, a lawyer at the Baker & McKenzie-affiliated BMVN International, a Hanoi-based law firm specializing in intellectual property and technology issues.

“Local Internet regulations do not specifically prohibit a local developer, such as Dong Nguyen, from providing his online game to an off-shore entity like Apple, unless the game contains illegal information or Dong Nguyen fails to comply with other local regulations,” Hung told the WSJ via email.